1. Field of the Invention
The present invention relates to a bearing type wheel for use in a car for a furnace or kiln, particularly for use in a car which moves through a car tunnel kiln whilst carrying thereon formed ceramic products so that the formed ceramic products are fired during movement of the car through the kiln.
2. Background of the Invention
In case of producing ceramic products continuously and in a large quantity, a tunnel kiln is used for firing formed ceramic products during movement of the formed ceramic products from the entrance to the exit of the kiln. To this end, the formed ceramic products are carried on a car which rolls on a track extending through the kiln.
A wheel of the car is of a roll bearing type and constituted by two inner rings installed on an axle of the car for rotation therewith, an intermediate ring installed on the axle of the car at a location intermediate between the inner rings, an outer ring of the width equal to the sum of the widths of the two inner rings and the intermediate ring and disposed concentrically of the inner rings and the intermediate ring, and a plurality of rollers interposed between the respective inner rings and the outer ring. The constituent parts of the wheel are made of metals similar to those of a bearing for a machine tool, for example, the rollers are made of SKD 61 (alloy steel according to Japanese Industrial Standard).
During movement of the car through the kiln, the wheels are exposed to the atmosphere of a high temperature. Accordingly, in case of a car whose wheels are entirely made of metal, a large force is necessitated for pulling the car since the function of the car is deteriorated due to the surface oxidation, plastic deformation and wearing. Further, the rollers finally lose its original form and are disabled to function properly, thus requiring replacement of the wheels and thus increasing the man-hour in the production of the ceramic products.